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Cautery protection circuit for a heart pacemaker

  • US 4,038,990 A
  • Filed: 11/19/1975
  • Issued: 08/02/1977
  • Est. Priority Date: 11/19/1975
  • Status: Expired due to Term
First Claim
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1. A bipolar heart pacemaker circuit comprising:

  • a. a pulse generator for generating a control signal at a desired rate according to that with which it is desired to stimulate a patient'"'"'s heart;

    b. output switch means responsive to the control signal for providing a heart stimulating output pulse to be applied by first and second leads to the patient'"'"'s heart; and

    c. a torroidal inductor including first and second inductors, each connected in-series with a corresponding one of said first and second leads and coupled together by a high coefficient of coupling to operate in a first mode in the presence of a cautery-inducted field, wherein the signals applied to said first and second inductors by the cautery-induced field induce fields in the same direction through said coupling and the inductances offered to the cautery-induced signals are correspondingly increased, and in a second, differential mode in response to the application of a pacemaker pulse signal wherein opposing fields are established through said coupling between said first and second inductors so that the inductances offered by said first and second inductors are significantly reduced, said torroidal inductor comprising a torroidal core having permeability in the order of 120, a bandwidth of not less than 10MHz and a resonant frequency of not less than 5MHz, whereby the impedance presented to said pulse generator is reduced and distortion applied to the heart stimulating output pulse is reduced.

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